Premium
Improved photosynthetic performance during severe drought in Nicotiana tabacum overexpressing a nonenergy conserving respiratory electron sink
Author(s) -
Dahal Keshav,
Martyn Greg D.,
Vanlerberghe Greg C.
Publication year - 2015
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13479
Subject(s) - alternative oxidase , photosynthesis , respiration , electron transport chain , nicotiana tabacum , chloroplast , photosystem i , biology , photosystem ii , cellular respiration , botany , photosynthetic efficiency , plant physiology , biochemistry , gene
Summary Chloroplasts have means to manage excess reducing power but these mechanisms may become restricted by rates of ATP turnover. Alternative oxidase ( AOX ) is a mitochondrial terminal oxidase that uncouples the consumption of reducing power from ATP synthesis. Physiological and biochemical analyses were used to compare respiration and photosynthesis of Nicotiana tabacum wild‐type ( WT ) plants with that of transgenic lines overexpressing AOX , under both well‐watered and drought stress conditions. With increasing drought severity, AOX overexpression acted to increase respiration in the light ( R L ) relative to WT . CO 2 and light response curves indicated that overexpression also improved photosynthetic performance relative to WT , as drought severity increased. This was not due to an effect of AOX amount on leaf water status or the development of the diffusive limitations that occur due to drought. Rather, AOX overexpression dampened photosystem stoichiometry adjustments and losses of key photosynthetic components that occurred in WT . The results indicate that AOX amount influences R L , particularly during severe drought, when cytochrome pathway respiration may become increasingly restricted. This impacts the chloroplast redox state, influencing how the photosynthetic apparatus responds to increasing drought severity. In particular, the development of biochemical limitations to photosynthesis are dampened in plants with increased nonenergy conserving R L .